This research program focuses upon behavioral and biobehavioral investigations of mental retardation and intellectual development. The basic problem investigated is the general area of learning and its facilitation. The ultimate objective is to identify and develop strategies and procedures for enhancing the adaptation of retarded persons to normal living circumstances. A related goal is to contribute to theories and the body of data concerning cognition, learning, and human development, with particular reference to the role of individual differences. The program is organized into three laboratories or research groups: Cognitive Processes, Comparative Development, and Experimental Analysis. A wide variety of research strategies is followed including basic laboratory experiments, observational studies in natural contexts, intervention or training procedures, longitudinal investigations, and single-subject experiments. Subjects for investigation are at-risk and normal babies, retarded people at all functional levels, peers and parents of retarded children, and rodents. Specific topics investigated are: Information processing capabilities among normal and retarded individuals, organization of semantic memory, patterns of infant-parent interactions, social interactions among retarded and normally developing children, analysis of discriminative and maintaining stimuli for aberrant and social responding, transfer or generalization of training, methods for teaching positive social behaviors, receptive and productive language, imitation learning, establishment of basic stimulus control, effects of prenatal stress on behavioral and physical development.